1. Field of the Invention
This invention generally relates to a running time maintenance monitor for, and method of, indicating that equipment operatively connected to the monitor is due for maintenance and, more particularly, to a programmable maintenance monitor operative at user-selected warning and maintenance times to respectively display warning and maintenance messages, a portion of at least one of the messages being individualized to a particular user. Additionally, a user-selected access code protects unauthorized tampering with the warning and maintenance times and the individualized message portion.
2. Description of the Prior Art
A programmable running time maintenance monitor for indicating when equipment, such as a fork lift truck, an automotive vehicle or the like, requiring periodic preventive maintenance, is due for such maintenance, was disclosed in U.S. Pat. No. 4,404,641. This known monitor permitted a user to readily set a maintenance time indicative of when the equipment was due for maintenance and, when the maintenance time was reached, a readout alerted a user. Additionally, a pre-maintenance or warning time indicative of an advance indication of when the equipment was due for maintenance was set and, when the warning time was reached, a readout alerted the user. Although this known monitor generally was satisfactory for its intended purpose, experience has shown that some users tampered with the warning and maintenance time settings and, hence, delayed the scheduled maintenance, thereby shortening, in some cases, the working lifetime of the equipment.
Other running time maintenance monitors were disclosed, for example, in the following patents:
______________________________________ U.S.L.P. No. 3,948,039 U.S.L.P. No. 4,180,724 U.S.L.P. No. 4,389,709 ______________________________________
Electronic timers employing electrolytic storage cells, wherein an electrical current was caused to flow through an electrolytic solution for designating an elapsed time after which equipment was ready for servicing, were disclosed, for example, in the following patents:
______________________________________ U.S.L.P. No. 3,355,731 U.S.L.P. No. 3,938,128 U.S.L.P. No. 3,546,693 U.S.L.P. No. 3,940,735 U.S.L.P. No. 3,603,880 U.S.L.P. No. 3,972,022 U.S.L.P. No. 3,903,736 U.S.L.P. No. 4,134,101 ______________________________________
Other apparatuses, which record and display data, such as operating time and/or other data, and/or electronic timers, were disclosed, for example, in the following references:
______________________________________ U.S.L.P. No. 4,338,512 U.S.L.P. No. 4,072,850 U.S.L.P. No. 3,758,756 U.S.L.P. No. 4,142,238 U.S.L.P. No. 4,025,774 U.S.L.P. No. 4,168,525 U.S.L.P. No. 4,031,363 U.S.L.P. No. 4,218,871 U.S.L.P. No. 4,135,246 U.S.L.P. No. 4,271,402 U.S.L.P. No. 4,159,531 U.S.L.P. No. 4,296,409 U.S.S.R. Patent No. 542,192 Japan Patent No. 54-144840 ______________________________________
Publication of Macon, Inc., entitled "Macon Central Lubrication Monitor", January 1980.
The use of a warning or disabling circuit was disclosed in U.S. Pat. No. 3,905,014.
The displays of the known maintenance monitors typically constituted audible or visible alarms or readouts to alert a user that maintenance was due. The conventional display merely lit up an indicator lamp and, in some cases, the lit lamp was located behind a light-transmissive panel on which a maintenance message was permanently affixed. Such permanent displays were the same for each user, and it would have been desirable to have had the user select, set and change, when desired, an individualized maintenance message appropriate for the particular user to thereby make compliance with the user's maintenance plan more effective.
Still further, it has been found for some equipment, such as electric fork lift trucks, which employ more than one motor, e.g. a drive motor for propelling the truck along the ground, a lift motor for lifting a load, and an auxiliary motor for tilting or projecting the lift carriage and/or for power steering, that the interval of time between deenergizing one motor and energizing another motor was lost in terms of accumulating the actual running time of the equipment.
It also has been found for running time maintenance monitors, particularly those which employ solid-state components, that a decrease in working lifetime of the solid-state components and/or data loss could occur when the running time was initiated by an equipment ignition switch which typically was cycled through an off-on-off-on cycle each time the equipment was started.